• Title/Summary/Keyword: Nanopowder

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Rapid Sintering and Synthesis of Nanostuctured FeCrAlSi-Al2O3 Composite by High-Frequency Induction Heating (고주파유도 가열에 의한 나노구조의 FeCrAlSi-Al2O3 복합재료의 합성 및 급속소결)

  • Du, Song Lee;Cho, Sung-Hun;Ko, In-Yong;Doh, Jung-Mann;Yoon, Jin-Kook;Park, Sang-Whan;Shon, In-Jin
    • Korean Journal of Metals and Materials
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    • v.49 no.3
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    • pp.231-236
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    • 2011
  • Nanopowder of $Fe_2O_3$, Al, Cr and Si was fabricated by high energy ball milling. A dense nanostuctured $A_2O_3$ and $6.06Fe_{0.33}Cr_{0.16}Al_{0.23}Si_{0.29}$ composite was simultaneously synthesized and consolidated using high frequency induction heated sintering method within 1 minute from mechanically activated powders of $Fe_2O_3$, Al, Cr and Si. The grain sizes of $Al_2O_3$ and $Fe_{0.33}Cr_{0.16}Al_{0.23}Si_{0.29}$ in composite are 80 and 18 nm, respectively.

A Study on the Characteristics of Silicon Nanopowders Produced by Transferred Type Arc Plasma Apparatus (이송식 아크플라즈마 장치에 의해 제조된 실리콘 나노분말의 특성에 대한 연구)

  • Kan, Woo-Seop;Park, Sang-Hee
    • Journal of the Korean Society of Industry Convergence
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    • v.24 no.6_2
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    • pp.909-917
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    • 2021
  • This study was carried out experimentally on the production and properties of silicon nanopowders characteristics using a transferred type arc plasma apparatus. To investigate the properties of silicon nanopowder, the purity of argon gas(99.999%, 99.9%) and the partial pressure ratio of nitrogen gas(0~90%) were varied. The total pressure in chamber is 400Torr and the silicon chunk amount used as raw material is 300g. The power supplied to the cathode to generate arc plasma was 9~12kW/h, and the electrode was made of tungsten and graphite with a diameter of 13mm. The particle size, impurity elements and powder evaporation rate of the silicon powder were analyzed using the XRD, FE-SEM, TEM and electronic scale. According to the purity of argon gas, the silicon evaporation rate and the particle size were similar, and impurities were generated more in the case of 99.9% purity than 99.999%. When argon gas and nitrogen gas were mixed in the chamber, the silicon evaporation rate and particle size increased as the partial pressure ratio of nitrogen gas increased. In particular, when the partial pressure ratio of nitrogen gas was 80%, the silicon evaporation rate 80g/h, and the particle size was about 80~100nm.

The Role of Endoscopic Interventions in Palliative Care for the Gastrointestinal Tumors (소화기 종양에 대한 내시경적 완화치료)

  • Hye Kang Kim;Dae Young Cheung
    • Journal of Digestive Cancer Research
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    • v.2 no.1
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    • pp.1-4
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    • 2014
  • Palliative care for cancer aims to relieve the discomfort and pain from the cancer itself and associated conditions. Gastrointestinal cancers originate from the tube like structure of gastrointestinal tract and cause complications such as obstruction, bleeding, adhesion, invasion, and perforation to adjacent organ. Recent advances in interventional endoscopy enables endoscopy physicians to do safe and effective care for gastrointestinal cancer patients. Endoscopic palliation includes stent, hemostasis, nutritional support and targeted drug delivery. Self expandable metallic stent is one of the most important modalities in gastrointestinal palliation. Through the endoscopy or over the wire pre-placed by endoscopy, stents restore the gastrointestinal luminal patency and relieve the obstructive condition. Endoscopic hemostasis is another important palliation in gastrointestinal cancer patients. Epinephrine injection, argon plasma coagulation and thermal cauterization are usual modalities for hemostasis. Histoacryl glue and fibrin glue are also available. Hemostatic nanopowder spray is newly reported effective in benign disease and is supposed to be effective also in cancer bleeding. Enteral feeding tubes including gastro- or jejunostomy and nosoduodenal tubes are placed by using endoscopic guidance. Enteral feeding tubes role as the route of easily absorbable or semi-digested nutrients and effectively maintain both patients calorie requirements and gut microenvironment. Photodynamic therapy is the one of the outstanding medical employments of photo-physics. Especially for superficial cancers in esophagus, photodynamic therapy is very useful in cancer removal and maintaining organ structure. In biliary neoplasm, photodynamic therapy is well known to be effective in cancer ablation and biliary ductal patency restoration. Targeted drug delivery is the lastest issue in palliative endoscopy. Debates and questions are still on the table. In this article, the role of endoscopic interventions in palliative care for the gastrointestinal tumors will be thoroughly reviewed.

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Effects of Mixing Ratio and Poling on Output Characteristics of BaTiO3-Poly Vinylidene Fluoride Composite Piezoelectric Generators (BaTiO3-Poly Vinylidene Fluoride 복합 압전발전기의 출력특성에 미치는 배합비와 분극의 효과)

  • Hee-Tae Kim;Sang-Shik Park
    • Korean Journal of Materials Research
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    • v.33 no.12
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    • pp.517-524
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    • 2023
  • BaTiO3-Poly vinylidene fluoride (PVDF) solution was prepared by adding 0~25 wt% BaTiO3 nanopowder and 10 wt% PVDF powder in solvent. BaTiO3-PVDF film was fabricated by spreading the solution on a glass with a doctor blade. The output performance increased with increasing BaTiO3 concentration. When the BaTiO3 concentration was 20 wt%, the output voltage and current were 4.98 V and 1.03 ㎂ at an applied force of 100 N. However, they decreased when the over 20 wt% BaTiO3 powder was added, due to the aggregation of particles. To enhance the output performance, the generator was poled with an electric field of 150~250 kV/cm at 100 ℃ for 12 h. The output performance increased with increasing electric field. The output voltage and current were 7.87 V and 2.5 ㎂ when poled with a 200 kV/cm electric field. This result seems likely to be caused by the c-axis alignment of the BaTiO3 after poling treatment. XRD patterns of the poled BaTiO3-PVDF films showed that the intensity of the (002) peak increased under high electric field. However, when the generator was poled with 250 kV/cm, the output performance of the generator degraded due to breakdown of the BaTiO3-PVDF film. When the generator was matched with 800 Ω resistance, the power density of the generator reached 1.74 mW/m2. The generator was able to charge a 10 ㎌ capacitor up to 1.11 V and turn on 10 red LEDs.

Synthesis of Carbon Coated Nickel Cobalt Sulfide Yolk-shell Microsphere and Their Application as Anode Materials for Sodium Ion Batteries (카본 코팅된 니켈-코발트 황화물의 요크쉘 입자 제조 및 소듐 이온 배터리의 음극 소재 적용)

  • Hyo Yeong Seo;Gi Dae Park
    • Journal of Powder Materials
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    • v.30 no.5
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    • pp.387-393
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    • 2023
  • Transition metal chalcogenides are promising cathode materials for next-generation battery systems, particularly sodium-ion batteries. Ni3Co6S8-pitch-derived carbon composite microspheres with a yolk-shell structure (Ni3Co6S8@C-YS) were synthesized through a three-step process: spray pyrolysis, pitch coating, and post-heat treatment process. Ni3Co6S8@C-YS exhibited an impressive reversible capacity of 525.2 mA h g-1 at a current density of 0.5 A g-1 over 50 cycles when employed as an anode material for sodium-ion batteries. However, Ni3Co6S8 yolk shell nanopowder (Ni3Co6S8-YS) without pitch-derived carbon demonstrated a continuous decrease in capacity during charging and discharging. The superior sodium-ion storage properties of Ni3Co6S8@C-YS were attributed to the pitch-derived carbon, which effectively adjusted the size and distribution of nanocrystals. The carbon-coated yolk-shell microspheres proposed here hold potential for various metal chalcogenide compounds and can be applied to various fields, including the energy storage field.

Synthesis of nano-sized Ga2O3 powders by polymerized complex method (착체중합법을 이용한 Ga2O3 나노 분말의 합성)

  • Jung, Jong-Yeol;Kim, Sang-Hun;Kang, Eun-Tae;Han, Kyu-Sung;Kim, Jin-Ho;Hwang, Kwang-Teak;Cho, Woo-Seok
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.23 no.6
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    • pp.302-308
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    • 2013
  • In this study, we report the synthesis and characteristics of gallium oxide ($Ga_2O_3$) nanoparticles prepared by the polymerized complex method. $Ga_2O_3$ nanoparticles were synthesized using $Ga(NO_3)_3$, ethylene glycol, and citric acid as the starting materials at a low temperature of $500{\sim}800^{\circ}C$. The temperature of the weight reduction by the loss of organic precursor was revealed using TG-DTA analysis. The crystal structural change of $Ga_2O_3$ nanoparticles by the annealing process was investigated by XRD analysis. The morphologies and the size distributions of $Ga_2O_3$ nanoparticles were analyzed using SEM.

Tungsten-Doped Titania Nanopowders - Their Chemical Vapor Synthesis and Photocatalytic Activity (텅스텐이 도핑된 티타니아 나노분말의 화학기상합성 및 광촉매 활성)

  • Park, Bo-In;Kang, Kae-Myung;Jie, Hyunseock;Song, Bong-Geun;Park, Jong-Ku;Cho, So-Hye
    • Journal of the Korean Institute of Gas
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    • v.16 no.6
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    • pp.143-147
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    • 2012
  • Photocatalytic properties of $TiO_2$ nanopowders has been received much attention due to their high potentials for environmental applications such as remediation of polluted environments. The $TiO_2$ nanopowders doped with metal or non-metal elements have been synthesized by variety methods such as flame method, chemical vapor synthesis, sol-gel, ion implantation, which affect a doping behavior in different ways resulting in different surface characteristics, leading to different photocatalytic activity. In addition to an effect of synthesis methods, the photocatalytic activity of $TiO_2$ nanopowders can be improved by subsequent heat-treatments. In this study, to obtain a highly efficient photocatalyst, we synthesized $TiO_2$ nanopowders doped with tungsten by the chemical vapor synthesis method (CVS) and determined their physical properties and photocatalytic activity, together with subsequent post-treatment in the range of $300^{\circ}C$ to $700^{\circ}C$.

Surface Characteristics and Antifouling Performance of Inorganic MnOx-WO3-TiO2 Nanopowder for Self-polishing Copolymer Paint Applications (무기계 MnOx-WO3-TiO2 나노분말의 표면특성 및 자기마모형 수지 적용성 평가)

  • Shin, Byeongkil;Park, Hyun
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.22 no.2
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    • pp.253-258
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    • 2016
  • The $MnO_x-WO_3-TiO_2$ nanoscale powders were synthesized by sol-gel method in order to prevent the biological fouling on the ships and offshore structures. Powder characteristics and antifouling performance were investigated with respect to the crystalline, microstructure and surface property for application in self-polishing copolymer resins. The high antifouling activity of $TiO_2$-system biocide was attributed to its redox potential and soluble metal ions originating from tungsten oxides according to the improvements in the powder characteristics. Based on their physio-chemical characterizations, the specific surface areas of powders were about $90m^2/g$ and the grain size was in the region 100 ~ 150 nm. Powder characteristics and surface properties were improved by the addition of $WO_3$. Antifouling performance were analyzed according to their surface properties and static immersion tests to determine the effects of the $TiO_2$-system compounds. The surface of 2 wt. % added sample was clean for 5 month. This may be attributed to the ability of $MnO_x-WO_3-TiO_2$ powders to act as a promoter in antifouling agents.

Synthesis of TiO2-xNx Using Thermal Plasma and Comparison of Photocatalytic Characteristics (열플라즈마에 의한 TiO2-xNx의 합성 및 광촉매 특성 비교)

  • Kim, Min-Hee;Park, Dong-Wha
    • Applied Chemistry for Engineering
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    • v.19 no.3
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    • pp.270-276
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    • 2008
  • $N_2$ doped $TiO_2$ nano-sized powder was prepared using a DC arc plasma jet and investigated with XRD, BET, SEM, TEM, and photo-catalytic decomposition. Recently the research interest about the nano-sized $TiO_2$ powder has been increased to improve its photo-catalytic activity for the removal of environmental pollutants. Nitrogen gas, reacting gas, and titanium tetrachloride ($TiCl_4$) were used as the raw materials and injected into the plasma reactor to synthesize the $N_2$ doped $TiO_2$ power. The particle size and XRD peaks of the synthesized powder were analyzed as a function of the flow rate of the nitrogen gas. Also, the characteristics of the photo-catalytic decomposition using the prepared powder were studied. For comparing the photo-catalytic decomposition performance of $TiO_2$ powder with that of $TiO_2$ coating, $TiO_2$ thin films were prepared by the spin coating and the pulsed laser deposition. For the results of the acetaldehyde decomposition, the photo-catalytic activity of $TiO_{2-x}N_x$ powder was higher than that of the pure $TiO_2$ powder in the visible light region. For the methylene blue decomposition, the decomposition efficiency of $TiO_2$ powder was also higher than that of $TiO_2$ film.